Heart disease is the leading cause of death in the industrialized world. Survival after myocardial infarction has improved considerably, but the cardiac remodeling that follows acute insults like ischemia/reperfusion injuries and chronic ones like hypertension and diabetes has led to a dramatic increase in the prevalence of heart failure. The failing heart displays numerous energetic abnormalities, including decreased expression of the transcriptional coactivator PGC-1a. The proven role of PGC-1a as a dominant regulator of mitochondrial biogenesis and respiration suggests that this molecule could represent a key control point for heart failure and open new therapeutic approaches. We and others have shown that PGC-1a -/- mice have important physiological cardiac abnormalities. Here, we will investigate the role of PGC-1a in cardiac disease. First, we will test if loss of PGC-1a exacerbates heart failure, by using transverse aortic constriction (TAG) in mice lacking PGC-1a. Preliminary data indicates a severe worsening of heart failure in the absence of PGC-1a. Conversely, we will also ask whether the development of heart failure can be ameliorated by mild, transgenic expression of PGC-1a in the heart. We also show in preliminary data that PGC-1a plays a key role in the suppression of reactive oxygen species (ROS) through expression of a broad program of ROS detoxification genes. Ischemia/reperfusion injury in the heart is thought to damage the heart in large part via generation of ROS. We will evaluate, using mice with gain or loss of PGC-1a, the role of this coactivator in ischemia/reperfusion injury in the heart. Analysis will be at both molecular and functional levels. Lastly, we will examine in detail the mechanisms by which PGC-1a plays a cardioprotective role by creating mutant alleles of this coactivator that selectively lose the ability to modulate either the ATP producing system or the ROS detoxification program. These alleles will be evaluated in a tissue culture setting and then knocked into the murine germline, and the subsequent effects on the heart will be examined. This proposed work, taken together, should critically evaluate the ability of the PGC-1 pathway to influence and perhaps ameliorate major forms of heart disease. This may lead to the development of a new class of therapeutics.